The present invention relates to gem-diesters and epoxidized derivatives thereof In a particular aspect, the present invention relates to re-workable adhesive compositions and methods for use thereof.
Epoxide resins are widely recognized as one of the most important types of thermosetting materials. Indeed, epoxides have been successfully used in a diverse array of applications, such as, for example, structural materials, adhesives, and coatings. The superior physical properties provided by cured epoxide resins (e.g., adhesive strength, toughness, resistance to degradation), combined with their relatively low cost, have allowed epoxides to displace other thermosetting chemistries in a variety of industries. In particular, epoxide resins have gained acceptance in the microelectronics industry in a variety of packaging applications, due to their low shrinkage upon cure, corrosion resistance, and good electrical properties. Accordingly, epoxides have been used in microelectronic packaging applications such as, for example, encapsulants, die-attach pastes, molding compounds, underfill materials, solder masks, and the like.
However, the very attributes which have allowed epoxides to gain such widespread acceptance in a variety of industries have, in certain respects, become liabilities. For example, in the microelectronics industry, the intractability of cured epoxide resins leaves little margin for error in the packaging of microelectronic components. Indeed, after the epoxide-based packaging material has been cured, it is exceedingly difficult to separate the component from its packaging material without damaging the component. Thus, if any error is detected in the semiconductor package post-cure, the entire assembly must often be discarded. Since the packaging step is the last stage in the manufacture of a microelectronic component, the loss of the component at this stage is especially taxing economically.
Moreover, recent environmental concerns have led to the development of recyclable products in a variety of industries. Traditionally, articles containing epoxide-based thermosetting adhesives have not been compatible with recycling protocols due to the high adhesive strength and intractability of the crosslinked thermoset network. Thus, as demand for recyclable products increases, there is simultaneously an increasing demand for thermosetting compositions which are re-workable (so as to be amenable to recycling protocols) yet maintain desirable properties such as high adhesive strength and toughness.
Epoxides have been developed which impart, at least to some degree, reworkable properties to a thermosetting resin produced therefrom. These epoxides contain labile groups such as secondary and tertiary esters (see C. Ober and H. Koerner, U.S. Pat. No. 5,973,033,
S. Yang et al, Chem. Mater., 1998, 10 (6), 1475, J. S. Chen et al, ACS Polymer Preprints 2000, 41(2), 1842, H. Li et al ACS PMSE Preprints 2000, 83, 563), aliphatic acetals (see A. Afzali-Ardakani et al, U.S. Pat. No. 5,512,613, A. Afzali-Ardakani et al, U.S. Pat. No. 5,560,934, S. Buchwalter et al, U.S. Pat. No. 5,932,682, J. Kuczynski and L. Mulholland, U.S. Pat. No. 6,008,266, S. Buchwalter et al, ACS PMSE Preprints 1995, 72, 450), and various carbamates (see L. Wang and C. Wong, J. Polym. Sci. Part A 1999, 37, 2991).
While these systems can provide network breakdown under certain conditions, there are several undesirable features associated with their use. Epoxidized secondary and tertiary esters are costly to produce and generally undergo network degradation at lower temperatures than is ideal. Epoxidized aliphatic acetals decompose only very slowly at high temperatures. Epoxidized carbamates are costly to produce and have the added undesirable effect of producing highly toxic isocyanates following thermolysis. In addition, the above classes of epoxy adhesives leave decomposition residues on the circuit board that are difficult to remove and thus make replacement more difficult than is desirable.
Thus, there is a need for reworkable epoxy adhesives are inexpensive to produce, do not generate toxic by-products on decomposition, and leave residues that are easy to clean. The present invention addresses these needs and further provides related advantages as will become apparent upon review of the specification and appended claims.
In accordance with the present invention, there are provided ethylenically unsaturated gem-diesters and epoxidized derivatives thereof. When cured, thermosets comprising invention ethylenically unsaturated gem-diesters and epoxidized derivatives thereof have thermally and/or chemically labile gem-diester groups interspersed throughout the crosslinked network. Thus, thermosets based on invention compounds can be easily reworked by simply heating the thermoset or by treatment with dilute acidic solutions or dilute basic solutions.
In accordance with a further embodiment of the present invention, there are provided adhesive compositions comprising invention compounds and methods for use thereof.
In additional embodiments of the present invention, there are provided methods for the preparation of epoxidized derivatives of gem-diesters, methods for adhesively attaching a device to a substrate, and methods for removing an adhesively attached device from a substrate.
In still further embodiments of the present invention, there are provided assemblies comprising first article(s) reversibly adhered to second article(s).